1. Field of the Invention
The present invention relates to inter-carrier-interference (ICI) cancellation, and in particular, it relates to an ICI cancellation iterative receiver and an ICI cancellation method in the OFDMA (Orthogonal Frequency Division Multiple Access) wireless communication system.
2. Description of the Related Art
The key drivers of demand for radio-based broadband access networks are massive growth in wireless and mobile communications, the emergence of multimedia applications, demand for high-speed Internet access, and the deregulation of the telecommunications industry. Due to their advantages, (e.g. in efficiently eliminating channel multi-path), OFDM (Orthogonal Frequency Division Multiplexing) is considered as one of the most attractive transmission techniques for future wireless multimedia communications in frequency selective channels. It has been adopted for the European Digital Audio Broadcasting (DAB) and Digital Video Terrestrial Broadcasting (DVB) standards, and it has just been standardized for new wireless LAN generations (such as IEEE 802.16a, and HIPERLAN). However, in real life situations, multicarrier transmission is subject to phase noise and the difference between the phase of the carrier and the phase of the local oscillator, a portion of which is untracked, and hence, an accurate prediction of the tolerable phase noise allows system or RF designers to relax specifications.
The OFDM system (e.g., the wireless broadband (WiBro) system based on the OFDMA wireless communication system or the high-speed portable (HP) Internet system) is sensitive to the time variant distortions in OFDM like oscillator phase noise, carrier and sampling frequency offset, and Doppler spread. Compared with the ICI introduced by the carrier frequency offset, Doppler-induced ICI appears to be more challenging. Meanwhile, phase noise, interpreted as a parasitic phase modulation in the oscillator's signal, is the difference between the phase of the carrier and the phase of the local oscillator, a portion of which is untracked, and BER (Bit Error Rate) performance is degraded due to the ICI induced by phase noise. Previous studies have qualified the effects of ICI on the system performance, which fails to totally eliminate ICI from the received signals.